Ice cloud formation potential by free tropospheric particles from long‐range transport over the Northern Atlantic Ocean

China, Swarup; Alpert, Peter A.; Zhang, Bo; Schum, Simeon; Džepina, K.; Wright, K.; Owen, R. C.; Fialho, Paulo; Mazzoleni, Lynn; Mazzoleni, Cláudio; Knopf, Daniel A.

doi:10.1002/2016jd025817

Cited by 49 publications

(139 citation statements)

References 113 publications

(195 reference statements)

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“…This study also suggests that dust particles coated with organic particles, which are observed within~75% of the ambient particles (Figure 4) can nucleate ice (see experiment A results; Figure 5) at water saturation conditions, These findings are consistent with many previous studies which investigated the ice nucleation ability of pure and organic-coated particles [58][59][60][61]. For example, Tobo et al (2012) [59] observed that at water-saturated conditions only sulfuric acid-coated kaolinite particles showed a reduction in ice nucleation efficiency and that the results were unaffected when these particles were coated with levoglucosan, a water-soluble organic compound.…”

Section: Inp Measurementssupporting

confidence: 91%

Immersion Freezing of Total Ambient Aerosols and Ice Residuals

Kulkarni

2018

Atmosphere

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This laboratory study evaluates an experimental set-up to study the immersion freezing properties of ice residuals (IRs) at a temperature ranging from −26 to −34 • C using two continuous-flow diffusion chamber-style ice nucleation chambers coupled with a virtual impactor and heat exchanger. Ice was nucleated on the total ambient aerosol through an immersion freezing mechanism in an ice nucleation chamber (chamber 1). The larger ice crystals formed in chamber 1 were separated and sublimated to obtain IRs, and the frozen fraction of these IRs was investigated in a second ice nucleation chamber (chamber 2). The ambient aerosol was sampled from a sampling site located in the Columbia Plateau region, WA, USA, which is subjected to frequent windblown dust events, and only particles less than 1.5 µm in diameter were investigated. Single-particle elemental composition analyses of the total ambient aerosols showed that the majority of the particles are dust particles coated with organic matter. This study demonstrated a capability to investigate the ice nucleation properties of IRs to better understand the nature of Ice Nucleating Particles (INPs) in the ambient atmosphere.

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Section: Inp Measurementssupporting

confidence: 91%

Immersion Freezing of Total Ambient Aerosols and Ice Residuals

Kulkarni

2018

Atmosphere

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“…Furthermore, it is possible that aging processes may not affect the ice nucleation ability of ambient particles given that the range of n s during FT background is similar to that of the BLI as seen in Figure 4. In a study by China et al (2017), a very small change in the ice nucleation activity between ambient particles was observed, despite differences in the particle chemical composition, source regions, and transport pathways. They concluded that aging did not play a significant role in the ice nucleation activity of ambient particles.…”

Section: Classification Of Inp Concentrationsmentioning

confidence: 95%

Background Free‐Tropospheric Ice Nucleating Particle Concentrations at Mixed‐Phase Cloud Conditions

Lacher¹,

DeMott

Levin

et al. 2018

JGR Atmospheres

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Clouds containing ice are vital for precipitation formation and are important in determining the Earth's radiative budget. However, primary formation of ice in clouds is not fully understood. In the presence of ice nucleating particles (INPs), the phase change to ice is promoted, but identification and quantification of INPs in a natural environment remains challenging because of their low numbers. In this paper, we quantify INP number concentrations in the free troposphere (FT) as measured at the High Altitude Research Station Jungfraujoch (JFJ), during the winter, spring, and summer of the years 2014–2017. INPs were measured at conditions relevant for mixed‐phase cloud formation at T = 241/242 K. To date, this is the longest timeline of semiregular measurements akin to online INP monitoring at this site and sampling conditions. We find that INP concentrations in the background FT are on average capped at 10/stdL (liter of air at standard conditions [T = 273 K and p = 1013 hPa]) with an interquartile range of 0.4–9.6/stdL, as compared to measurements during times when other air mass origins (e.g., Sahara or marine boundary layer) prevailed. Elevated concentrations were measured in the field campaigns of 2016, which might be due to enhanced influence from Saharan dust and marine boundary layer air arriving at the JFJ. The upper limit of INP concentrations in the background FT is supported by measurements performed at similar conditions, but at different locations in the FT, where we find INP concentrations to be below 13/stdL most of the time.

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“…However, the increased concentration of methane sulfonic acid (MSA) in PMO-2 relative to PMO-1 and PMO-3 suggests some degree of marine influence. To estimate this, we used the non-background subtracted sodium concentration as an upper limit to estimate sea salt sulfate according to the method described in Chow et al (2015), this led to a maximum sea salt sulfate contribution of 25 %. The influence of marine sources supports boundary layer transport.…”

Section: Flexpart Numerical Simulationsmentioning

confidence: 99%

Molecular and physical characteristics of aerosol at a remote free troposphere site: implications for atmospheric aging

et al. 2018

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Aerosol properties are transformed by atmospheric processes during long-range transport and play a key role in the Earth's radiative balance. To understand the molecular and physical characteristics of free tropospheric aerosol, we studied samples collected at the Pico Mountain Observatory in the North Atlantic. The observatory is located in the marine free troposphere at 2225 m above sea level, on Pico Island in the Azores archipelago. The site is ideal for the study of long-range-transported free tropospheric aerosol with minimal local influence. Three aerosol samples with elevated organic carbon concentrations were selected for detailed analysis. FLEXPART retroplumes indicated that two of the samples were influenced by North American wildfire emissions transported in the free troposphere and one by North American outflow mainly transported within the marine boundary layer. Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry was used to determine the detailed molecular composition of the samples. Thousands of molecular formulas were assigned to each of the individual samples. On average ∼ 60 % of the molecular formulas contained only carbon, hydrogen, and oxygen atoms (CHO), ∼ 30 % contained nitrogen (CHNO), and ∼ 10 % contained sulfur (CHOS). The molecular formula compositions of the two wildfire-influenced aerosol samples transported mainly in the free troposphere had relatively low average O/C ratios (0.48 ± 0.13 and 0.45 ± 0.11) despite the 7-10 days of transport time according to FLEXPART. In contrast, the molecular composition of the North American out-flow transported mainly in the boundary layer had a higher average O/C ratio (0.57±0.17) with 3 days of transport time. To better understand the difference between free tropospheric transport and boundary layer transport, the meteorological conditions along the FLEXPART simulated transport pathways were extracted from the Global Forecast System analysis for the model grids. We used the extracted meteorological conditions and the observed molecular chemistry to predict the relative-humidity-dependent glass transition temperatures (T g ) of the aerosol components. Comparisons of the T g to the ambient temperature indicated that a majority of the organic aerosol components transported in the free troposphere were more viscous and therefore less susceptible to oxidation than the organic aerosol components transported in the boundary layer. Although the number of observations is limited, the results suggest that biomass burning organic aerosol injected into the free troposphere is more persistent than organic aerosol in the boundary layer having broader implications for aerosol aging.

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Ice cloud formation potential by free tropospheric particles from long‐range transport over the Northern Atlantic Ocean

Cited by 49 publications

References 113 publications

Immersion Freezing of Total Ambient Aerosols and Ice Residuals

Immersion Freezing of Total Ambient Aerosols and Ice Residuals

Background Free‐Tropospheric Ice Nucleating Particle Concentrations at Mixed‐Phase Cloud Conditions

Molecular and physical characteristics of aerosol at a remote free troposphere site: implications for atmospheric aging

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